1. Field of the Invention
The present invention relates generally to the field of lithotripters used for noninvasive fragmentation of concrements in living beings. More specifically, the present inventions disclose an improved electrode for lithotripters in which the discharge tips can be easily removed and replaced while maintaining the tolerance of the spark gap intermediate the discharge tips.
2. Description of Related Art
Conventional extra-corporeal lithotripters utilize shock waves to noninvasively fragment concrements within a patient. Most lithotripters are comprised of an electrode which generates a spark at a spark gap intermediate discharge tips. The spark is usually positioned within a reflector filled with a fluid. The presence of the spark in the fluid generates acoustic shock waves as a certain amount of water is flashed to steam. The shock wave passes through the reflector and through tissues of the patient until the concrement is contacted. A plurality of shock waves has been found effective at disintegrating many concrements.
The electrodes are usually constructed with an inner conductor which is surrounded by an insulative layer applied as a liquid and allowed to solidify about the inner conductor. The inner conductor terminates at a first electrode tip which extends from the insulative layer at a distal end of the inner conductor and insulative layer. An opposing second electrode tip is located collinearly with the first electrode tip to provide the spark gap there between. The first and second electrode tips are usually symmetrically located relative to one another about the spark gap. A cage provides a conductor and necessary structure to support the tip and to conduct electricity from an outer housing about the insulative layer to the second electrode tip. A clip is usually positioned about the housing to connect the electrode with a reflector and an electric supply.
Rapid and frequent discharges of energy across the electrode tips of the spark gap has been found to erode and/or deteriorate the electrode tips. Since the gap between the electrode tips is usually provided within relatively precise tolerances, most electrodes are not provided with an ability to replace either of the two opposing electrode tips. One attempt to provide an improved electrode can be seen in U.S. Pat. No. 5,420,473 which shows an insulative layer about the inner conductor equipped with threads which cooperate with inner threads on the housing so that the distance between opposing electrodes can be set to relatively precise tolerances simply by screwing the two together until a stop is contacted.
While the '473 patent reference shows a product that is an improvement over the prior art, this device still requires the replacement of the entire inner conductor/insulative layer assembly whenever the discharge electrode tip is degraded since the insulative layer must be machined off the inner doctor and a new one re-applied after replacing the electrode tip.
Accordingly an improved electrode is needed to overcome the limitations of the prior art.